1. Field of the Invention
The present invention relates to a method of evaluating an ion irradiation effect, a process simulator and a device simulator. More specifically, it relates to a method of evaluating an ion irradiation effect, which is distinctive in an arrangement for evaluating the effect of ion irradiation in ion implantation or ion etching with high accuracy, a process simulator and device simulator.
2. Description of the Related Art
The ion implantation technique has been used as a method of forming an impurity-doped region in a semiconductor device for a step of forming a source and a drain of a MOSFET, etc. Various simulation methods have been proposed for the purpose of estimating an impurity distribution resulting from ion implantation like this with high accuracy in advance (see e.g. JP-A-2004-079656).
There are various kinds of parameters for performing such simulation, which require numerical values measured in fact. For example, the distribution of an actual impurity concentration after ion implantation has been measured in reality by use of e.g. SIMS (Secondary Ion Mass Spectrometry) or the like.
In the case where SIMS is used to perform composition analysis of a thin film, etc., a standard sample composed of different materials alternately stacked into a multilayered form is used to calibrate the resolution of a direction of the depth, and the calibration is performed based on an ion intensity distribution of the standard sample.
However, some standard samples like this have a problem that because of having two or more layers of different materials, the samples have a so-called interface effect developed in the vicinity of an interface between the layers of different materials, which can expand or shrink an ion intensity distribution extraordinarily.
Hence, it has been proposed to use a standard sample which has alternately-stacked atomic layers of different isotopes, but common in element species (see e.g. JP-A-06-273289).
As for an isotope standard sample like this, isotopes are slightly different in atomic mass number, but entirely identical in chemical property. Therefore it has been reported that the interface effect and matrix effect disappear, and the resolution in a direction of the depth can be improved in accuracy.
On the other hand, a silicon (Si) substrate is damaged by ion implantation, and therefore the evaluation of such damage has been made by use of a channeling method in Rutherford backscattering spectrometry or a transmission electron microscope (see e.g. Journal of Applied Physics, Vol. 88, p. 3993, 2000).
Likewise, such damage will be caused in nanometer-scale ion beam machining by means of FIB (Focused Ion Beam) technique.
However, a conventional method of evaluating a damage has had a problem that it is difficult to quantitatively know the extent to which the silicon atoms in a portion damaged by ion irradiation are displaced.
Further, in the case of analysis by SIMS, a sample is analyzed while being etched by ions. Therefore, there has been a problem that it is difficult to evaluate what influences an effect by a physical force caused by ion etching, e.g. ion beam induced diffusion has on a composition distribution and a silicon lattice.
Therefore, the invention aims at evaluating an influence which ion irradiation exerts on atoms constituting a substrate with high accuracy.